1. Field of the Invention
The present invention relates to an ink jet printing method and apparatus, and more specifically, to so called margin-less printing (hereinafter also referred as no edge blank printing), in which a printing medium such as a printing sheet is printed without forming any edge blank spaces on the printing medium.
2. Description of the Related Art
In an ink jet printing apparatus such as an ink jet printer, a platen is provided at an opposite portion to a printing head. The platen determines a positional relationship between a printing medium transported thereon and the printing head that ejects ink to the printing medium. For example, the platen has a plurality of platen ribs arranged on a top surface thereof in a scanning direction of the printing head. Supported on the tops of the platen ribs, the printing medium can be transported while maintaining a fixed distance from the printing head.
On the other hand, the ink jet printer can accomplish high-image-quality printing comparable to a silver salt photography. There correspondingly has been a growing demand for margin-less printing in which printing is carried out on the printing medium that is glossy like silver salt photographs In recent years, ink jet printers having the corresponding functions for the margin-less printing have been provided.
When the ink jet printer is used for the margin-less printing, it is necessary that ink is essentially ejected also to an area extending out from an edge of the printing medium to prevent a blank space from occurring on an edge portion of the printing medium. That is, errors may occur while the printing medium is being transported or errors in the size of the printing medium may occur in connection with cutting accuracy. Accordingly, to allow for such errors, ink is generally ejected to an area extending out from the position of the edge of the transported printing medium (see FIG. 11).
The ink ejected to the extending area is desirably corrected. For this purpose, for example, as shown in FIG. 11, a gap N3004 is formed in the above described platen rib M3003 so as to have a predetermined distance along a scanning range of the printing head, in a direction in which the printing medium is transported. An ink-absorbing member (not shown) is also provided at the bottom of the gap M3003. Further, an ink-absorbing member is provided on the platen at predetermined locations in a width direction of the printing medium corresponding to the scanning direction of the printing head, and over an area corresponding to a range within which ejection openings of the printing head are arranged. These arrangements for correcting ink enable ink ejected out from four edges of the printing medium to be corrected, thereby achieving margin-less printing to the printing medium.
However, when such no edge blank printing is executed notably at an edge area (including an area extending out from the edge of the printing medium in the direction in which it is transported and an area located inside this edge) located close to the edge of the printing medium, a large amount of ink mist may be generated, resulting in worse printing condition. The inventors have thus found that certain measures must be taken to reduce the amount of possible ink mist.
That is, when a normal area different from the edge area is printed, a distance between the printing medium, a target of ejected ink, and the printing head is relatively short, and then a distance over which the ejected ink flies is also short. Accordingly, a relatively small amount of ink mist may scatter or float without reaching the printing medium. However, when the edge area is printed, a distance between the ink-absorbing member, the target of ejected ink which is ejected out from the edge of the printing medium, and the printing head is relatively long, and then a distance over which the ejected ink flies is also long. Accordingly, a relatively large amount of ink mist may scatter or float without reaching the absorbing member. Thus, when the edge area is printed, certain measures must be taken to reduce the amount of mist. If no measures are taken for the mist, ink mist adhering to the printing medium or the platen ribs is likely to contaminate the printing medium. Further, ink mist adhering to rollers or gears is likely to disturb the normal operation of the rollers or gears.